1. FIELD OF THE INVENTION
The present invention relates to a valve operating system for internal combustion engines, comprising a drive cam follower operatively connected to an engine valve, a free cam follower capable of operation independent of the drive cam follower relative to the engine valve, the cam followers being adjacently disposed and arranged to operate the valve in mutually different modes in response to rotation of a cam shaft, a connection change-over mechanism is provided between the cam followers and is capable of changing-over the interconnection and disconnection thereof, and resilient biasing means is provided between the free cam follower and the engine body for resiliently urging the free cam follower toward the cam shaft.
2. DESCRIPTION OF THE PRIOR ART
Such valve operating system for internal combustion engines is conventionally know, for example, from Japanese patent application Laid-open No. 19911/86.
However, in order to reduce the power for driving each cam follower in such valve operating system, it is necessary to reduce the inertial weight of each cam follower to the utmost. In order to reduce the inertial weight of the free cam follower, it is desirable to place the sliding point of the urging piston in the resiliently biasing means as close as possible to the pivot point of the free cam follower. In the prior art system, however, the sliding point of the urging piston on the free cam follower cannot be disposed in sufficient proximity to the pivoting point of the free cam follower due to the need for avoidance of any interference of the urging piston with the pivoting point of the free cam follower.